The present invention relates to an apparatus utilizing a charged-particle beam to analyze a specimen such as an electron probe microanalyzer.
In conventional electron probe microanalysis, an image of a specimen such as an image produced from secondary electrons is displayed on the viewing screen of a CRT. A mark consisting of dots is superimposed on the image of the specimen to specify or indicate the analysis point.
The aforementioned image of the specimen is obtained by scanning the electron beam while the electron probe microanalyzer is in scanning mode. The operator observes the image of the specimen and looks for a location of concern. Then the operator moves the mark to specify an analyzed point with the mark.
If the operator subsequently shifts the analyzer from scanning mode to analysis mode, then the electron beam is fixed on a point on the specimen which corresponds to the position on the specimen image specified by the mark. The electrons strike the specimen at the analyzed point and diffuse into the specimen. X-rays, secondary electrons, backscattered electrons, etc., are emitted until the energy of the incident electron is lost.
FIG. 1 is a cross-sectional view of a specimen, taken across an analyzed point. Some regions from which x-rays or electrons as described above are emitted are shown. The specimen and an incident electron beam are denoted by S and EB, respectively. Secondary electrons are emitted from a region, e.sub.s. Backscattered electrons emanate from a region e.sub.r. X-rays are produced from a region x. In electron probe microanalysis, the intensity and the wavelengths of x-rays generated from the region x are analyzed and so the region x undergoes analysis. As can be seen from FIG. 1, the region x producing x-rays are generally considerably larger than the other regions e.sub.s and e.sub.r producing secondary electrons and backscattered electrons. It is known that the size of the x-ray emission region x varies greatly, depending on the voltage at which the incident electron beam EB is accelerated and also on the mean atomic number of the constituents of the specimen S. The region e.sub.r emitting backscattered electrons has a similar but more moderate tendency.
A secondary electron image or a backscattered electron image is normally employed as a specimen image to look for a region to be analyzed. Since the secondary electron emissive region e.sub.s and the backscattered electron emissive region e.sub.r are smaller than the x-ray emissive region x as described above, the specimen image is created with a resolution higher than the spatial resolution of x-ray analysis. The aforementioned mark superimposed on such a high-resolution specimen image has only a given size. Therefore, the mark provides no information about the size of the analyzed region, though the mark indicates the position of the analyzed region.